Lamp filament winding machine



April 25, 1967 5. J. MIKINA ETAL LAMP FILAMENT WINDING MACHINE s Sheets-Sheet 3 Filed Feb. 20, 1964 FIG. 3.

FIG. 5.

INVENTORS 45 Z w M W M w m J 0,, Y5 Em m m5 S United States Patent 3,315,508 LAMP FILAMENT WINDING MACHINE Stanley J. Mikina, Penn Hills, and Merrideth D. Wilson, Monroeville, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 20, 1964, Ser. No. 346,297 12 Claims. (CI. 72-66) The present invention relates to a machine for the winding of fine wire coils and, more particularly, to such a machine which produces filaments for electric lamps at a greater rate than heretofore and with increased quality of the finished product.

Machines for the winding of lamp filaments are now well known in the art but such machines have heretofore been limited in their production rate because of several factors. For example, it is necessary that a certain tension be applied to the filament 'wire and hence the spooled bobbin from which the relatively fine tungsten wire is unwound must necessarily have a slight drag. This is to preclude too free a rotation and thus eliminate the possibility of looping or tangling of the wire while maintaining the required tension which may be as much as 50 grams. In these prior type winding machines, the spin velocity of the bobbin relative to its shaft approximates one percent the speed of the winding head, depending, of course upon the particular wire size, bobbin diameter, and diameter of the mandrel wire, which in a large percentage of instances represents a bobbin speed velocity of about 100 r.p.m. at a winding head speed of 8000 rpm. This relatively low spin speed of the bobbin has been heretofore accomplished by the employment of small and accurate bushing-shaft clearances and the use of a relatively high viscosity lubricant therebetween in order to develop the above-noted required tensions.

The disadvantages of attempting to maintain these required tensions in the foregoing manner resides in the fact that the etfecttive bobbin clearances may change in an erratic and unpredictable manner due to trapped dirt and dust particles on the shaft or in the lubricant and also the viscosity of such lubricant is itself a sensitive function of its temperature. Both effects in time may result in an alteration in wire tension from the desired value. In addition, the subsequent aging of the lubricant, with a change in its chemical composition, as well as its viscosity, entirely independent of temperature, or shaft vibration during high speed winding, can cause a deviation in the tension values.

Another major factor limiting the speed of previous type filament winding machines and materially affecting the quality of the finished product has been the manner of heating the bridge pin. Such bridge pin is utilized to heat the filament wire, as well as the mandrel wire, for the purpose of annealing the tungsten filament wire in order to make the inside diameter of the formed helix conform more accurately to mandrel wire diameter without cracking or breaking of the fine filament wire. Heretofore, however, such bridge pin which is of relatively low electrical resistance, has been heated by an electric current supplied thereto by brushes, resulting in the voltage drop at the brushes consuming about seventy percent of the applied voltage. Inasmuch as these brushes, as well as their associated commutator rings, are subject to vibration and wear with usage, a wide variation in the voltage drop across such brushes inherently occurs. Since the heating of the bridge pin is proportional to the square of the voltage drop thereacross and this is directly afiected by the variation in voltage drop across the brushes, considerable variations in the bridge pin temperature occurs. Such variations are inherently reflected in corresponding 3,315,508 Patented Apr. 25, 1967 variations in tungsten wire annealing and degree of conformity of the filament helix to its mandrel.

It is accordingly the primary object of the present invention to overcome the difficulties inherent in prior art filament winding machines by maintaining the filament wire at a uniform preset tension and by heating the bridge pin to a definite substantially constant temperature.

Another object of the present invention is the provision of a filament winding machine wherein the filament wire is maintained under a substantially constant preselected tension by means of a magnetic field.

A further object of the present invention is the provision of a filament winding machine wherein the bridge pin is heated to a definite substantially constant temperature by making such bridge pin a part of an alternating current generator.

The foregoing objects of the present invention, together with other objects which will become obvious to those skilled in the art from the following description, are achieved by providing a machine for the winding of filaments for electric lamps wherein a definite preselected tension of the fine filament wire is maintained by provision of a drag disc on the Winding head which is subjected to an eddy current torque produced by two electromagnets carried by a frame. The drag disc rotates in the air-gap between the two electromagnets and hence is subjected to the magnetic field generated thereby. This produces a pure torque on the drag disc with no lateral electromagnetic force to load the supporting bearings of either the drag disc or the magnet frame. By restraining rotation of the magnet frame by a spiral spring, a definite measurement of the drag torque is obtained on a scale which may be graduated in grams to give a linear scale of wire tension. In order to prevent the filament wire bobbin from over-running the winding head upon deceleration to lower speeds, a centrifugal clutch is utilized to apply a decelerating torque to the bobbin to thus maintain filament-wire tension during the short stopping pe riod. For the purpose of maintaining the bridge pin at a substantially constant temperature to assure uniformity in the winding of the filament helix, such bridge pin is made an integral part of an alternating current generator which itself is part of the winding head. Heating of the bridge pin to a desired magnitude is accomplished by varying the generator field which is indicated on a field ammeter calibrated in terms of bridge pin amperes.

The present invention can be readily understood by reference to the accompanying drawings wherein:

FIGURE 1 is a fragmentary top plan view of a filament winding machine constructed in accordance with the present invention and showing the electric circuitry in conjunction therewith;

FIG. 2 is a sectional view taken on the line II-II of FIG. 1 looking in the direction indicated by the arrows;

FIG. 3 is a sectional view taken on the line IIIHI of FIG. 2;

FIG. 4 is a sectional view taken on the line IV-IV of FIG. 2;

FIG. 5 is a sectional view taken on the line VV of FIG. 2;

FIG. 6 is a fragmentary view similar to FIG. 5 but on a slightly larger scale; and

FIG. 7 is a sectional view taken on the line VH-VII of FIG. 6.

Referring now to the drawings in detail, the filament winding machine as therein shown and described comprises a base 5 having mounted thereon a gear housing 6. Such housing is provided with a sleeve 7 carrying bearings 8 at each end thereof in which the hollow main drive shaft 9 of the machine is journalled, see FIG. 2. Interiordrel advances.

1 7 a V ly of the housing 6, this main drive shaft 9 is provided with an integral worm 10 meshing with a gear 12 carried 'by a shaft 13 extending to the turns per inch (t.p.i.)

V filament. One end of this drive shaft 9 carries a combination drive-pulley and flywheel 15 while the other end carries a flywheel 16 which supports a frame 17 carrying a wire guide tube 18 and an alternating cur-rent generator armature 19. The combination drive-pulley-flywheel 15, together with the main shaft 9 and parts carried thereby and comprising the winding head, are rotated by an endless belt 20 extending from an induction motor (not shown) with the two flywheels 15 and 16 serving to minimize speed fluctuations due to momentary variations either in the driving torque or the load torque.

Coaxially disposed within the hollow main shaft 9 is another hollow-bore shaft 22 journalled on bearings 23 and on which the bobbin 24 is mounted from which the fine tungsten filament wire 25 is unspooled. Such bobbin 24, while slidable axially on its supporting shaft 22, nevertheless applies a drive torque to such shaft through axial drive pins 26, which connect the bobbin 24 to a bobbin hub brakedrum 27 rigidly secured to the shaft 22, with such drive torque being equal to the filament wire tension times its radius from the bobbin axis as the moment arm. The filament wire '25 upon leaving the bobbin 24 passes through a wire feeding means comprising the guide tube 18 and is then fed to a wedge-shaped space between the nose of a tungsten-carbide-tipped mandrel guide or bearing 28 and a heating means comprising the heated bridge pin 29 where such fine filament wire is wound in the form of a spring-like helix 30 upon the mandrel wire 14 by rotation of the winding head.

The mandrel wire 14 advances axially through the ho-llow-bore shaft 22 and outwardly of the mandrel guide 28 at a rate of advance determined by the revolutions per minute speed of the winding head and the worm 10 and gear 12, which drive the conventional t.p.i. capstan in order to fix the turns per inch of the filament helix 30, as

hereinbefore mentioned. By reference more particularly to FIG. 7, it will be noted that the tungstencarbide-tipped mandrel guide 28 isaxially biased by a coil spring 32 against the heated bridge pin 29 with the [latter being positioned normal to the axis of the mandre-lwire 14 and extending above the latter, so that the filament wire 25 coming 'out of the guide tube 18 passes on the inside of the bridge pin 29 andabove the mandrel wire 14 as it is wound upon the latter. Continued ope-ration of the apparatus will in due time cause a few parallel slanted grooves to be cut in the bridge pin surface past which the coiled filament moves, which grooves will have a pitch equal'to the pitch of filament winding 30. Likewise a single groove will eventually be cut in the heated bridge pin'29 on the side against which the filament wire 25 is pressed by the force of die spring 32. However, instead of being detrimental these grooves are actually an aid to the formation of the filament helix since they create an unvarying geometry of filament restain right at the critical point of helix formation. a

By providing a given bridge pin temperature mandrel wire tension, and a fixed as hereinafter described, the only remaining factor affecting uniformity of the filamenthelix is that of the actual tension of the filament wire 25 itself.

Accordingly, in order to control the tension of such filament wire 25 thedriving torque on the hollow-bore shaft 22, produced by the tension of filament wire 25 acting through its bobbin radius moment arm, is resisted at the other end of such shaft by the eddy current torque of an electrically conducting and preferably non-magnetic drag disc 33 of copper, or the like. Such disc is rigidly secured wire tension torque.

In order to generate the eddy current torque imposed upon the drag disc 33' two electromagnet coil means or assemblies 34 and 35 are provided each of which comprises an exciting coil 36 and an iron core terminating in pole pieces 37 and 38 with the drag disc 33 being rotatable in the air gap therebetween. Such electromagnet assemblies 34 and 35 are secured to a circular frame 39 journalled upon bearings 48 and carried by a short shaft 42 coaxially disposed relative to shaft 22 and the drag disc 33 affixed thereto. The frame supporting shaft 42 is secured to an upright 43 extending from the base 5 and a stop-pin 44 projects from such upright parallel to the frame shaft 42 for the purpose of limiting axial rotation on the magnet frame 39 together with its electromagnet assemblies 34 and 35, and such rotation itself is restrained by a spiral spring 45 formed of two Phosphor bronze wires. 7

By reference particularly to FIGS. 1 and 3, it will be noted that the two electromagnet assemblies 34 and 35 are located diametrically opposite to each other and they porting bearings 23 of the drag disc shaft 22 or the bearings of the magnet frame 39. The magnet exciting coils 36 are energized with direct current from a first power supply means or source 46(FIG. 1) formed by power rectifier circuits which is connected to the exciting coils 36 by the Phosphor bronze spring wires to thus avoid indication errors by elimination of slip.

' rings and current leads with internal friction. The magnitude of the current supplied to the magnet exciting coils 36 by the power rectifier circuits is controlled by V a variable resistor. 51 (FIG. 1). Moreover, the currentconducting spring wires 45 are designed for an angular, travel of the circular or drum-shaped magnet frame 39 7 through an angle of approximately as limited by the stop-pin 44, with graduations 47 onthe frame drum giving an indication in terms of grams of wire tension.

of drag disc 33 since the angular deflection of the magnet frame 39 against the opposing stiffness'of spiral spring bobbin 24 at the same rate as the winding head. Accordingly, during deceleration tolower speeds the bobbin 24 Y could overrun the main drive shaft 9 with suflicient momentum to unspool the filament wire 25 at a faster rate than it is wound upon the mandrel 14. To avoid this condition with possible ensuing tangling of the filament wire 25 a centrifugal clutch is provided by the present invention for automatically applying a friction decelerating torque to the bob'bin 24 to maintain filament tension during the short stopping period.

vThis centrifugal clutch, as shown particularly in FIGS. 1 and 4, comprises two diametrically opposed brake shoes 48 biased by coil springs 49 into contact with the peripheral surface of the bobbin hubbrake drum 27. Since the brake shoe shafts 50 fit into holes provided in the winding head supporting frame 17 they rotate with such Although such graduations 47 maybe in terms of wire tension it actually constitutes a measurement of the torque frame and winding head with the mass of each brake shoe 48 being such that the centrifugal force causes radial sliding movement of the brake shoe shafts 50 together with a slight compression of the springs 49, so that the brake springs 49 apply sufficient brake torque to the bobbin assembly to effect the desired deceleration yet allow slippage at a permissible value of wire tension to allow coil winding without breakage of the fine filament wire 25 during the acceleration and deceleration period.

Accordingly, in the Winding machine of the present invention designed to operate at 12,000 r.p.m., the mass of each brake shoe 48 is selected to cause each shoe to throw out radially and disengage the bobbin hub brake drum 27 at a winding head speed of 5000 rpm. During the normal winding operation which is well above such speed, the tension of filament wire 25 is determined by the drag disc 33, while below the 5000 r.p.m. speed during acceleration or deceleration the wire tension represents the sum of the drag disc effect and .the brake shoe torque, with the former decreasing to zero linearly with speed while the latter increases from zero as the square of the speed ditference between 5000 rpm. and the actual speed, until it reaches maximum braking torque at standstill.

Referring now to the alternating current generator which in accordance with the present invention heats the bridge pin 29 to a uniform temperature, it will be seen more particularly from FIGS. 1 and 5 that the laminated armature coil means 19' of such generator is secured to and hence rotates coaxially with the winding head frame 17. Such laminated armature 19 is disposed between stationary pole pieces 52 and 53 of an clectromagnet supported by an upright 54 extending from the base 5 and having its exciting coil 55 connected to the second power supply means or direct current supply source 46 and constituting the power rectifier circuits shown in FIG. 1 with the magnitude of the current controlled by a variable resistor 56. As shown in FIGS. 5 and 6, the center leg of the laminated armature 19 is provided with a single layer winding 57 having its respective end terminals connected directly to opposite ends of the low resistance bridge pin 29. During rotation of the armature 19 the periodic reversals of magnetic flux through the rotating armature coil 57 generates an alternating current and since the bridge pin 29 is of low resistance, the armature coil 57 needs only to be of the single layer of comparatively few turns as shown, to develop a relatively high heating current which is passed through the bridge pin 29. By way of example, an armature winding of only eighteen turns is suflicient to cause a current of 14 amperes to how through the bridge pin 29.-

For optimum matching of the generator to the load, the armature reactance Lw must be made equal to the bridge pin resistance. That is:

Where N=number of armature turns,

' A=effective cross-sectional area of armature air-gap, cm. AEcross-sectional iron area of armature, w=spin frequency, radius/sec, h=total length of air-gap, cm., R =bridge pin resistance, ohms.

The generated voltage is:

BAmN volts B=fiux density, gauss.

These two relations govern the design of the generator. In conformity therewith, the amature reaction due to the without departing load current is minimized in the usually manner by making the generator air-gap h large and using a proportionally large number of ampere-turns in the field to establish the required flux density in the armature iron. The wave form of the output voltage under load is made nearly sinusoidal by making the pole tips of armature 19 in the form of cylindrical segments, as shown in FIG. 6, which tips span the shortest distance betWeen the field pole pieces 52 and 53, as seen particularly in FIG. 5. The magnitude of the bridge pin heating is adjusted by varying the generator field through operation of the variable resistor 56 and an indication of such setting is given by a field ammeter 58 calibrated in terms of bridge pin amperes. Also, the position of the bridge pin 29 tangent to the mandrel wire 14 is adjustable as is customary in the art.

It should thus become apparent to those skilled in the art that a machine for the winding of filaments for electric lamps is herein shown and described which produces such filaments at a considerably greater rate than heretofore with increased quality of the finished product. Such increased production rate has been made possible in accordance with the present invention by the provision of a controllable preselected drag torque which eliminates the possibility of uncontrolled unspooling the fine filament wire from its bobbin by application of a definite preselected tension thereto. Moreover, uniformity of the finished filament coil is achieved by maintaining the bridge pin at a constant preselected temperature to thus assure uniform formation of the fine filament-wire helix on its mandrel wire by connecting such bridge pin as a load across the output of an alternating current generator forming an integral part of the winding head of the machine.

As a possible alternative embodiment, the electromagnet assemblies 34 and 35, as shown in FIG. 1, could be replaced by permanent magnets. In such case, adjustment of the drag could be made by moving the permanent magnets in and out so that the effective speed and radius of the disc 33 would vary, depending on the position of the permanent magnets.

Although one specific embodiment of the present invention has been herein shown and described, it is to be understood that still further modifications may be made from the spirit and scope of the invention.

a We claim:

1. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together With a bobbin supplying a fine filament wire, and a bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) and clutch means carried by said winding head and automatically operable upon acceleration or deceleration of the latter below a predetermined speed to apply a decelerating torque to said bobbin and prevent overriding thereof relative to said winding head and thereby maintaining sufiicient tension of said fine filament Wire to eliminate possible tangling thereof.

2. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a Winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament wire, and a bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) drag torque means carried by said Winding head and rotatable therewith for applying a drag torque to said bobbin to maintain a uniform tension on the fine filament wire and prevent undesirable unspooling thereof from said bobbin upon any variation in rotation speed of said winding head,

(c) control means carried by said machine adjacent said drag torque means and operable to cause the V latter to apply a preselected drag torque to the bobbin carried by said winding head,

(d) and means carried by said winding head and operable upon deceleration of the latter to decrease the speed of rotation of said bobbin and prevent overriding therebetween and thereby maintain suflicient tension of said fine filament wire to eliminate tangling thereof.

3. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin connected to a bobbin hub brake drum and operable to supply a fine filament wire, and a bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) drag torque means carried by said winding head and rotatable therewith for applying a drag torque to said bobbin to maintain a uniform tension on the fine filament wire and prevent undesirable unspooiing thereof from said bobbin upon any variation in rotation speed of said winding head,

() control means carried by said machine adjacent said drag torque means and operable to cause the latter to apply a preselected drag torque to the bobbin carried by said winding head,

(d) and a centrifugal clutch carried by said winding head and engageable with said bobbin hub brake drum to apply a decelerating torque to said rotating bobbin upon deceleration of said winding head below a predetermined speed thereby preventing possible overriding therebetween during deceleration and maintaining sufficient tension of said fine filament Wire to eliminate possible tangling thereof.

4. In a filament coiling machine for the winding of fine Wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with -a bobbin supplying a fine filamentwire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such Wire in the form of a tight helix upon said mandrel wire;

(b) and means connected to said bridge pin for heating the same to a uniform temperature comprising an electric current generator carried by said winding head and operable by rotation of the latter to produce electrical energy of substantially constant magnitude which is supplied to said bridge pin.

5. In a filament coiling machine for the winding of fine wire' filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced; (b) means connected to said bridge pin for heating the same to a uniform temperature comprising an alternating curent generator provided with an exciting coil and an armature winding, carried by said 8 winding head and operable by rotation of the latter to cause its armature winding to generate an alternating current for heating said bridge pin to a substantially constant temperature,

(c) and a variable voltage source connectable by an operator to said generator exciting coil to energize the latter with a preselected voltage to cause said armature winding to supply a preselected current to said bridge pin to control the magnitude of its COD-1 stant temperature.

6. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of (a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament Wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) means connected to said bridge pin for heating the same to a uniform temperature comprising an alternating current generator provided with an exciting coil and an armature winding carried by said winding head and operable by rotation of the latter to cause its armature winding to generate an alternating current for heating said bridge pin to a substanti-ally constant temperature;

(c) a variable voltage source connectable by an operator to said generator exciting coil to energize the latter with a preselected voltage to cause said armature winding to supply a preselected current to said bridge pin to control the magnitude of its temperature,

(d) and a meter connected to said variable voltage source for measuring the current supplied thereby to said generator exciting coil and graduated in terms of temperature to record the temperature of said bridge pin.

7. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together With a bobbin supplying a fine filament wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind. such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) drag torque means carried by said winding head and rotatable therewith for applying a drag torque to said bobbin to maintain a uniform tension on the fine filament Wire and prevent undesirable unspooling thereof from said bobbin upon any variation in rotation speed of said winding head,

(c)- control means carried by said machine adjacent said drag torque means and operable to cause the latter to apply a preselected drag torque to the bobbin carried by said winding head,

(d) and means connected to said bridge pin for heating the same to a uniform temperature comprising alternating current generator carried by said winding head and operable by rotation of the latter to produce electrical energy of substantially constant preselected magnitude which is supplied to said bridge pin. 7 8. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such wire in the form of a tight helix upon said mandrel wire as it is advanced;

(b) a centrifugal clutch carried by said winding head and operable to apply a decelerating torque to said rotating bobbin upon deceleration of said winding head below a predetermined speed thereby preventing possible overriding therebetween during deceleration and maintaining sufiicient tension of said fine filament wire to eliminate possible tangling thereof,

(c) and means connected to said bridge pin for heating the same to a uniform temperature comprising an alternating current generator carried by said winding head and operable by rotation of the latter to produce electrical energy of substantially constant preselected magnitude which is supplied to said bridge pin.

9. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such wire in the form of a tight helix upon said mandrel wire;

(b) drag torque means carried by said winding head and rotatable therewith for applying a drag torque to said bobbin to maintain a uniform tension on the fine filament wire and prevent undesirable unspooling thereof from said bobbin upon any variation in rotation speed of said winding head,

(c) a centrifugal clutch carried by said winding head and operable to apply a decelerating torque to said rotating bobbin upon deceleration of said winding head below a predetermined speed thereby preventing possible overriding therebetween during deceleration and maintaining suflicient tension of said fine filament wire to eliminate possible tangling thereof,

(d) and means connected to said bridge pin for heating it to a uniform temperature comprising an alternating current generator carried by said winding head and operable by rotation thereof to produce electrical energy of substantially constant preselected magnitude which is supplied to said bridge pin.

10. In a filament coiling machine for the winding of fine wire filaments for electric lamps, the combination of:

(a) a winding head for supporting a mandrel guide through which a mandrel wire is advanced, together with a bobbin supplying a fine filament wire, and a heated bridge pin, said head being operable upon rotation to draw the fine filament wire from said bobbin across said heated bridge pin and wind such wire in the form of a tight helix upon said mandrel wire,

(b) a non-magnetic and electrically conducting drag disc carried by said winding head and rotatable therewith for applying a drag torque to said bobbin to maintain a uniform tension on the fine filament wire and prevent undesirable unspooling thereof from said bobbin upon any variation in rotation speed of said winding head,

(c) an electromagnet comprising a pair of exciting coils each having coaxially disposed pole pieces diametrically positioned relative to each other and parallel to the axis of said non-magnetic drag disc and with said disc disposed in the air-gap formed between said pole pieces to cause said drag disc to impose a drag torque on said bobbin to maintain a preselected tension on said fine filament wire at all rotary speeds of said winding head,

((1) a centrifugal clutch carried by said winding head and operable to apply a decelerating torque to said rotating bobbin upon deceleration of said winding head below a predetermined speed thereby preventing possible overriding therebetween during deceleration and maintaining suflicient tension of said fine filament wire to eliminate possible tangling thereof,

(e) means connected to said bridge pin for heating the same to a uniform temperature comprising an alternating current generator provided with an exciting coil and an armature Winding carried by said winding head and operable by rotation of the latter to cause its armature winding to generate an alternating current for heating said bridge pin to a substantially constant temperature,

(f) and a variable voltage source connectable by an operator to said generator exciting coil to energize the latter with a preselected voltage to cause said armature winding to supply a preselected current to said bridge pin to control the magnitude of its constant temperature.

1-1. In combination with a filament coiling apparatus comprising means for advancing a mandrel at a predetermined rate of speed, rotatable coiling means for rotating about the advancing mandrel and at a predetermined rate a bobbin of the wire to be wound as a helix about such mandrel, wire feeding means for directing the wire wound from the bobbin onto the advancing mandrel, and a heating means for heating the wire as it is wound onto the advancing mandrel, the improvement which comprises:

(a) armature coil means having output terminals and aflixed to said coiling means and rotatable therewith;

(b) energizable magnetic field generating means affixed with respect to and proximate said armature coil means, said magnetic field generating means and said armature coil means comprising a generator;

(c) said heating means comprising a resistive load connected across the output terminals of said armature coil; and

(d) adjustable power supply means for energizing said magnetic field generating means to set at a predetermined value the power consumed by said heating means; whereby the amount which the wire is heated on being wound is carefully controlled.

12. In combination with a filament coiling apparatus comprising means for advancing a mandrel at a predetermined rate of speed, rotatable coiling means for rotating about the advancing mandrel and at a predetermined rapid rate a bobbin of wire to be Wound as a helix about such mandrel, wire feeding means for directing the wire wound from the bobbin onto the advancing mandrel, and a heating means for heating the wire as it is wound onto the advancing mandrel, the improvement which comprises:

(a) electrically conducting disc means connected to and rotatable with said bobbin;

(b) electromagnetic coil means energized by first power supply means and having spaced pole pieces between which is generated a magnetic field, said pole pieces spaced on either side of said rotatable disc means to generate therein eddy currents and a drag force which acts against the rotation of said bobbin;

(c) said first power supply means being adjustable to set at a predetermined value the drag force on said disc means and said connected bobbin to prevent free rotation thereof;

(d) an armature coil means having output terminals and afiixed to said coiling means and rotatable therewith;

(e) energizable magnetic field generating means affixed with respect to and proximate said armature coil means, said magnetic field generating means and said armature coil means comprising a generator;

(f) said heating means comprising a resistive load References Cited by the Examiner connected across the output terminals of said arma- UNITED STATES PATENTS g f fif i 0 d W 1 s f en r 1,855,876 4/1932 Barker 72--66 g S g g 2 e 5 2,163,565 6/1939 Thomas 72--66 glzln sal ma netlc e eneratmg means to set 2,667,204 1/1954 Jaycox H at a predetermined value the power consumed by said heating means to carefully control the amount CHARLES LANHAM, Pnmmy Examine"- which the wire is heated on being wound. L. A. LARSON, Assistant Examiner. 

2. IN A FILAMENT COILING MACHINE FOR THE WINDING OF FINE WIRE FILAMENTS FOR ELECTRIC LAMPS, THE COMBINATION OF: (A) A WINDING HEAD FOR SUPPORTING A MANDREL GUIDE THROUGH WHICH A MANDREL WIRE IS ADVANCED, TOGETHER WITH A BOBBIN SUPPLYING A FINE FILAMENT WIRE, AND A BRIDGE PIN, SAID HEAD BEING OPERABLE UPON ROTATION TO DRAW THE FINE FILAMENT WIRE FROM SAID BOBBIN ACROSS SAID BRIDGE PIN AND WIND SUCH WIRE IN THE FORM OF A TIGHT HELIX UPON SAID MANDREL WIRE AS IT IS ADVANCED; (B) DRAG TORQUE MEANS CARRIED BY SAID WINDING HEAD AND ROTATABLE THEREWITH FOR APPLYING A DRAG TORQUE TO SAID BOBBIN TO MAINTAIN A UNIFORM TENSION ON THE FINE FILAMENT WIRE AND PREVENT UNDESIRABLE UNSPOOLING THEREOF FROM SAID BOBBIN UPON ANY VARIATION IN ROTATION SPEED OF SAID WINDING HEAD, (C) CONTROL MEANS CARRIED BY SAID MACHINE ADJACENT SAID DRAG TORQUE MEANS AND OPERABLE TO CAUSE THE LATTER TO APPLY A PRESELECTED DRAG TORQUE TO THE BOBBIN CARRIED BY SAID WINDING HEAD, (D) AND MEANS CARRIED BY SAID WINDING HEAD AND OPERABLE UPON DECELERATION OF THE LATTER TO DECREASE THE SPEED OF ROTATION OF SAID BOBBIN AND PREVENT OVERRIDING THEREBETWEEN AND THEREBY MAINTAIN SUFFICIENT TENSION OF SAID FINE FILAMENT WIRE TO ELIMINATE TANGLING THEREOF. 